The buoyant densities, rho-zero, of a large number of proteins in CsCl solutions will be measured in the ultracentrifuge. This data will be correlated with amino acid compositions. Buoyant titrations of four proteins will be completed. Buoyant densities of native and fully denatured proteins will be measured. A number of new experimental and analytical methods will be developed incuding the use of Spinco's gradient beads to determine rho-zero's of proteins, the contribution of volume changes on ionization to Delta rho-zero's and a study of pH gradients. A variety of chemically modified proteins will be prepared and their rho-zero measured to quantitate the contribution of those residues to rho-zero's of the native protein. The buoyant behavior of a number of synthetic copolypeptides and mixtures of ionizable homopolypeptides will be measured. This data will be compared with data already obtained for pure homopolypeptides to determine independence of the contribution of residues to the macromolecule's density. Thermodynamic data for CsCl at low temperatures will be measured isopiestically and refractive indices obtained to permit the use of the density gradient method at 5 degrees centigrade. Dilatometric, potentiometric and electrophoretic measurements are proposed to determine partial specific volumes, ionization behavior and isoelectric points in concentrated CsCl solutions.